With increasing development of science and technology, the functions and operating speeds of various electronic devices are gradually enhanced. For maintaining normal operations, a forced convection mechanism (e.g. a fan) is installed in the electronic device to dissipate heat that is generated by the electronic components of the electronic device. Consequently, the electronic device can be maintained at the normal operating temperature.
FIG. 1 is a schematic exploded view illustrating a conventional fan device. As shown in FIG. 1, the conventional fan device 1 includes an impeller 11, a rotor structure 121, a stator structure 122, a circuit board 123 and a motor base 13. The circuit board 123 is configured to change the direction of the magnetic pole current flowing through the stator structure 122. Due to the change of the magnetic pole current, the rotor structure 121 is rotated. As the rotor structure 121 is rotated, the impeller 11 is simultaneously rotated with the rotor structure 121.
As the electronic device is developed toward high performance and miniaturization, the heat-dissipating efficacy of the electronic device should be taken into consideration. For example, as the demands on the performance of the servers of a server system are gradually increased, the heat generated by the server system is increased. For effectively dissipating the heat, a single fan device is usually replaced by two fan devices in series. Under this circumstance, the fabricating cost is largely increased. In views of cost-effectiveness, it is important to increase the heat-dissipating efficacy of the single fan devices.
Conventionally, the increase of the rotating speed of the fan device may enhance the performance of the fan device by using a large current to drive rotation of the motor. Under this circumstance, the number or volume of the electronic components mounted on the circuit board of the fan device needs to be increased. Since the number or volume of the electronic components mounted on the circuit board is increased, a larger-sized circuit board should be used to increase the current capacity. Since the circuit board 123 is installed between the winding assembly of the stator structure 122 and the motor base 13, the larger-sized circuit board may block the airflow channel. If the airflow amount is reduced, the performance of the fan device is deteriorated.
For preventing the circuit board from hindering the airflow channel, the circuit board may be installed outside the fan frame of the fan device. However, since the circuit board is installed outside the fan frame, the volume of the server or other electronic device should be increased to provide a larger space to accommodate the circuit board. Under this circumstance, the applications of the fan device for the client are restricted and the market acceptance thereof is insufficient. Therefore, there is a need of providing a fan device with an improved fan frame in order to increase the space utilization of the circuit board and the performance of the fan device without hindering the airflow channel and increasing the overall volume of the fan device.